Locking Device And Method Employing A Posted Member To Control Positioning Of A Stabilization Member Of A Bone Stabilization System

ABSTRACT

A locking device and method are provided for a bone stabilization system which includes a bone anchor, a coupling mechanism and a stabilization member, wherein the coupling mechanism couples the stabilization member to the bone anchor. The locking device includes a seating member and a posted member. The seating member is operatively associated with the coupling mechanism for securing the stabilization member within the coupling mechanism, and is configured with an opening therein. The posted member, which includes an interface member and a post extending therefrom, is configured for disposition between the seating member and the stabilization member with the post extending therefrom being received into the opening in the seating member when the seating member is employed to secure the stabilization member within the coupling mechanism. The post is sized to engage and facilitate control of the stabilization member as the seating member operatively engages the coupling mechanism.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application contains subject matter which is related to the subjectmatter of the following applications, which are hereby incorporatedherein by reference in their entirety:

-   “Multi-Axial Bone Attachment Assembly”, Coates et al., U.S. Ser. No.    10/870,011, filed Jun. 17, 2004, and published on Dec. 22, 2005 as    Patent Application Publication No. US 2005/0283157 A1;-   “Coupling Assemblies for Spinal Implants”, Justis et al., U.S. Ser.    No. 11/197,799, filed Jan. 31, 2006;-   “Force Limiting Coupling Assemblies for Spinal Implants”, Justis et    al., U.S. Ser. No. 11/112,221, filed Jan. 31, 2006;-   “Bone Anchor System Utilizing a Molded Coupling Member for Coupling    a Bone Anchor to a Stabilization Member and Method Therefor”, Dewey    et al., U.S. Ser. No. 11/414,878, filed May 1, 2006, (Attorney    Docket No. P23147.00);-   “Locking Device and Method, for Use in a Bone Stabilization System,    Employing a Set Screw Member and Deformable Saddle Member”, Jeffrey    Moore, U.S. Ser. No. 11/414,879, filed May 1, 2006, (Attorney Docket    No. P24289.00); and-   “Locking Device and Method, for Use in a Bone Stabilization System,    Employing a Break-Away Interface Member Rigidly Coupled to Seating    Member,” Dewey et al., U.S. Ser. No. ______, co-filed herewith,    (Attorney Docket No. P25223.00).

TECHNICAL FIELD

The present invention relates generally to orthopaedic implants used forthe correction of spinal injuries or deformities, and more specifically,but not exclusively, concerns apparatuses and methods for fixing aparticular segment or level of the spine, to allow for deformitycorrection or healing thereof.

BACKGROUND OF THE INVENTION

In the field of spinal surgery, it is known to place implants intovertebrae for a number of reasons, including: (a) correcting an abnormalcurvature of the spine; (b) to maintain appropriate vertebral spacingand provide support for broken or otherwise injured vertebrae; and (c)to perform other treatments in the spinal column.

Typical spinal implant or bone stabilization systems utilize a rod asthe support and stabilizing element. In such a system, a series of twoor more bone fasteners are inserted into two or more vertebrae to beinstrumented. A rod or other stabilizing device is then placed within orattached to the head(s) of the bone fastener(s), or is placed within acoupling device that links the rod and the head(s) of the bonefastener(s). The connections between these multiple components are thensecured, thereby fixing the supporting construct to multiple levels inthe spinal column.

To advance the state of orthopaedic implants, enhancement to such bonestabilization systems are believed desirable, and are addressed herein.

SUMMARY OF THE INVENTION

Briefly summarized, the present invention comprises in one aspect alocking device for use in a bone stabilization system. The bonestabilization system includes a bone anchor, a coupling mechanism and astabilization member. The coupling mechanism is configured to couple thestabilization member to the bone anchor. The locking device includes aseating member and a posted member. The seating member is operativelyassociated with the coupling mechanism for securing the stabilizationmember within the coupling mechanism, and is configured with at leastone opening therein. The posted member includes an interface member andat least one post extending therefrom. The posted member is configuredfor disposition between the seating member and the stabilization memberwith the at least one post extending from the interface member beingreceived into the at least one opening of the seating member when theseating member is employed to secure the stabilization member within thecoupling mechanism. Further, the at least one post is sized tofacilitate control of the stabilization member as the seating memberoperatively engages the coupling mechanism to secure the stabilizationmember within the coupling mechanism with the posted member disposedbetween the seating member and the stabilization member.

In another aspect, a bone stabilization system is provided whichincludes a bone anchor, a stabilization member and a coupling mechanism.The coupling mechanism is configured to operatively connect the boneanchor and the stabilization member. The bone stabilization systemfurther includes a locking device which operatively connects to thecoupling mechanism to secure the stabilization member within thecoupling mechanism. The locking device includes a seating member and aposted member. The seating member is operatively associated with thecoupling mechanism for securing the stabilization member within thecoupling mechanism, and is configured with at least one opening therein.The posted member includes an interface member and at least one postextending therefrom. The posted member is configured for dispositionbetween the seating member and the stabilization member with the atleast one post extending from the interface member being received intothe at least one opening of the seating member when the seating memberis employed to secure the stabilization member within the couplingmechanism. Advantageously, the at least one post is sized to facilitatecontrol of the stabilization member as the seating member operativelyengages the coupling mechanism to secure the stabilization member withinthe coupling mechanism with the posted member disposed between theseating member and the stabilization member.

In yet another aspect, a surgical drive tool is presented forinserting/extracting a locking device of a bone stabilization system.The bone stabilization system includes a bone anchor, a couplingmechanism, and a stabilization member, wherein the coupling mechanism isconfigured to couple the stabilization member to the bone anchor. Thelocking device includes a seating member operatively associated with thecoupling mechanism for securing the stabilization member within thecoupling mechanism. The seating member is configured with at least oneopening therein. The locking device further includes a posted member,which includes an interface member and at least one post extendingtherefrom. The posted member is configured for disposition between theseating member and the stabilization member with the at least one postextending from the interface member being received into the at least oneopening of the seating member when the seating member is employed tosecure the stabilization member within the coupling mechanism.

The surgical drive tool comprises a first component and a secondcomponent. The first component is configured to operatively engage theseating member to facilitate positioning of the seating member withinthe coupling mechanism, while the second component is configured tooperatively engage the at least one post of the posted member tofacilitate maintaining the posted member fixed and in physical contactwith the stabilization member as the first component is employed tosecure the seating member within the coupling mechanism, and therebysecure the stabilization member within the coupling mechanism betweenthe posted member and the coupling mechanism.

In a further aspect, a method for stabilizing a spinal column ispresented. This method includes: providing a bone stabilization systemcomprising a bone anchor, a stabilization member, a coupling mechanism,and a locking device, wherein the coupling mechanism is configured tocouple the stabilization member to the bone anchor, and the lockingdevice is operatively associated with the coupling mechanism, andwherein the locking device further comprises a seating member configuredto threadably engage the coupling mechanism and a posted memberconfigured to control the stabilization member as the seating memberthreadably engages the coupling mechanism, the posted member comprisingan interface member and at least one post extending therefrom, andwherein the seating member includes at least one opening therein;positioning the stabilization member in the coupling mechanism;positioning the posted member with the at least one post thereof withinthe at least one opening of the seating member, and threading theseating member into the coupling mechanism while holding the at leastone post of the posted member fixed and in physical contact with thestabilization member, thereby maintaining control of the stabilizationmember as the seating member engages the coupling mechanism; andcontinuing to threadably advance the seating member into the couplingmechanism, thereby causing the posted member to become fixed between theseating member and the stabilization member, and securing thestabilization member between the posted member and the couplingmechanism.

Further, additional features and advantages are realized through thetechniques of the present invention. Other embodiments and aspects ofthe invention are described in detail herein and are considered a partof the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other objects, features andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a perspective view of one embodiment of a bone stabilizationsystem, in accordance with an aspect of the present invention;

FIG. 2 is a perspective view of one embodiment of a coupling mechanism,in accordance with an aspect of the present invention;

FIG. 3 is a cross-sectional elevational view of the coupling mechanismof FIG. 2, taken along line 3-3, in accordance with an aspect of thepresent invention;

FIG. 4 is a partial elevational view of one embodiment of a bonestabilization system employing a locking device comprising a seatingmember and a posted member, shown with the posted member in operativeposition and the seating member exploded from the coupling mechanism, inaccordance with an aspect of the present invention;

FIG. 4A is a partial elevational view of the bone stabilization systemof FIG. 4, showing the seating member operatively engaging the couplingmechanism with the posted member disposed between the seating member andthe stabilization member, in accordance with an aspect of the presentinvention;

FIG. 5 is an elevational view of a bone stabilization system employinganother embodiment of a locking device wherein the seating member isbeginning threaded engagement with the coupling mechanism, and theposted member is disposed in operative position between thestabilization member and the seating member, in accordance with anaspect of the present invention;

FIG. 5A is a partial elevational view of the bone stabilization systemof FIG. 5 after the seating member is fully threadably engaged with thecoupling mechanism to secure the stabilization member between thecoupling mechanism and the posted member, in accordance with an aspectof the present invention;

FIG. 6 is an elevational view of an alternate embodiment of a bonestabilization system employing a polyaxial coupling mechanism-to-boneanchor interface, and a locking device such as illustrated above inconnection with FIGS. 4-4A, in accordance with an aspect of the presentinvention;

FIG. 7A is an elevational view of one embodiment of a posted member, inaccordance with an aspect of the present invention;

FIG. 7B is an isometric view of the posted member of FIG. 7A, inaccordance with an aspect of the present invention;

FIG. 7C is an elevational view of an alternate embodiment of a postedmember wherein one or more protrusions extend from the distal surface ofthe posted member, in accordance with an aspect of the presentinvention;

FIG. 8A is an elevational view of another embodiment of a posted member,in accordance with an aspect of the present invention;

FIG. 8B is an elevational view of still another embodiment of a postedmember, in accordance with an aspect of the present invention;

FIG. 9A is an elevational view of a further embodiment of a postedmember, in accordance with an aspect of the present invention;

FIG. 9B is an elevational view of another embodiment of a posted member,in accordance with an aspect of the present invention;

FIG. 10A is a top plan view of yet another embodiment of a postedmember, in accordance with an aspect of the present invention;

FIG. 10B is a top plan view of a further embodiment of a posted member,in accordance with an aspect of the present invention;

FIG. 10C is an isometric view of the posted member of FIG. 10B, inaccordance with an aspect of the present invention;

FIG. 11 is an elevational view of one embodiment of a seating member,with a partial post of a posted member disposed therein, in accordancewith an aspect of the present invention;

FIG. 11A is an elevational view of an alternate embodiment of a seatingmember, with a partial post of a posted member disposed therein, inaccordance with an aspect of the present invention;

FIG. 12A is an isometric view of another embodiment of a seating member,in accordance with an aspect of the present invention;

FIG. 12B is a top plan view of the seating member of FIG. 12A, inaccordance with an aspect of the present invention;

FIG. 12C is a top plan view of a further embodiment of a seating member,in accordance with an aspect of the present invention;

FIG. 13 is an elevational view of a bone stabilization system andsurgical drive tool operatively engaging the locking device of the bonestabilization system, in accordance with an aspect of the presentinvention;

FIG. 14 is a partial elevational view of another embodiment of a bonestabilization device and surgical drive tool operatively engaging thelocking device of the bone stabilization system, in accordance with anaspect of the present invention;

FIG. 14A is a cross-sectional elevational view of the surgical drivetool FIG. 14 taken along line 14-14, in accordance with an aspect of thepresent invention;

FIG. 15 is an exploded view of an alternate embodiment of a surgicaldrive tool for engaging a locking device of a bone stabilization system,in accordance with an aspect of the present invention; and

FIG. 15A is an isometric view of the inner shaft component of thesurgical drive tool of FIG. 15, in accordance with an aspect of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Generally stated, presented herein is an enhanced locking device for abone stabilization or anchor system, as well as surgical drive tools forinserting/extracting the locking device and surgical methods forstabilizing a column employing a bone stabilization system and theenhanced locking device. The bone stabilization system includes a boneanchor (e.g., a screw), a coupling mechanism (e.g., an integral head)and a stabilization member (e.g., a rod), wherein the coupling mechanismis configured to couple the stabilization member to the bone anchor. Theenhanced locking device includes a seating member (e.g., a setscrew) anda posted member. The seating member is operatively associated with thecoupling mechanism for securing the stabilization member within thecoupling mechanism, and includes at least one opening therein. Theposted member includes an interface member and at least one postextending therefrom. The posted member is configured for dispositionbetween the seating member and the stabilization member with the atleast one post extending from the interface member being received intothe at least one opening of the seating member when the seating memberis employed to secure the stabilization member within the couplingmechanism. The at least one post is sized to facilitate handling of theseparate seating member and posted member pieces, as well as control ofthe stabilization member as the seating member operatively engages thecoupling mechanism to secure the stabilization member within thecoupling mechanism with the posted member disposed between the seatingmember and the stabilization member. Various embodiments of the seatingmember and posted member, as well as various embodiments of the surgicaldrive tool are described below with reference to FIGS. 4-15A. Oneembodiment of a bone stabilization system is first presented, however,with reference to FIGS. 1-3.

FIG. 1 depicts one embodiment of a bone stabilization system 60, whichincludes a coupling mechanism 10, a locking device 20, (comprising, inthis embodiment, a seating member 22 and a saddle member 50), astabilization member 30, and a bone anchor 40. When used in a spine tosecure multiple levels of the spinal column, each bone anchor 40 isplaced within an individual vertebrae, and a coupling mechanism 10 isattached to the implanted bone anchor 40. Following placement ofmultiple bone anchors and coupling mechanisms, an appropriatelydimensioned stabilization member 30, which spans one or more levels ofthe affected vertebral region, is placed within the coupling mechanisms10 and secured in place employing multiple locking devices. In thisinitial embodiment, locking device 20 includes seating member 22 andsaddle member 50. When the locking device is in use, stabilizationmember 30 is frictionally held in place between coupling mechanism 10and seating member 22 by saddle member 50.

In one implementation, the locking device may be formed with adeformable saddle member 50 to reduce the resultant stresses realized instabilization member 30 by decreasing the generation of surface stressrisers when fixed within coupling mechanism 10 by being fabricated fromthe same or similar material as stabilization member 30 and having aconcave distal interface surface that further deforms to the shape ofstabilization member 30.

With further reference to FIGS. 2 and 3, coupling mechanism 10 of bonestabilization system 60 includes a channel 14 defined by a seat 13 and apair of coupling arms 11. Coupling arms 11, which are disposed paralleland project in an upward manner from seat 13, together with seat 13 forma U-shaped channel 14, which is appropriately sized to receivestabilization member 30. The internal walls of coupling arms 11 includeinternal threads 12 or alternatively an internal cam surface (not shown)to engage external threads of seating member 22. Typically, at least onethrough hole 15 is located directly below seat 13 in coupling mechanism10. In one approach, a bone anchor is inserted into hole 15 prior to theplacement of the stabilization member. The longitudinal axis of the boneanchor may be at a fixed angle relative to coupling mechanism 10following insertion into hole 15 or be allowed to pivot within hole 15.Hole 15 may be counter bored, counter sunk, slotted, have a sphericalseat, keyed or any combination or derivation of these manufacturingtechniques, to allow the top portion of the anchor head to sit below theseat floor 16.

In this example, seating member 22 threadably engages with internalthreads 12 of coupling mechanism 10, although it should be understood bythose skilled in the art that other configurations are possible,including a seating member configured to include an external cam surface(not shown) that engages with an internal cam surface (not shown)located on the internal surface of coupling arms 11. In an unlockedposition, stabilization member can move freely within channel 14. Whenin a locked position, with the locking device substantially engaged withinternal threads 12 of the coupling mechanism, pressure or a compressiveforce is applied across the distal interface surface of the saddlemember onto the stabilization member.

Stabilization member 30 (see FIG. 1) is typically shaped as an elongateand continuous orthopaedic implant, for example, in the shape of a rod.Alternative stabilization members may include, but are not limited toplates, bars, tethers, cables, elastic structures and dynamicstabilization members (not shown). Stabilization member 30 may befabricated from a plastic material, such as a polyetheretherketone(PEEK) polymer. Alternatively, stabilization member 30 may be fabricatedfrom a material comprising carbon fiber composite polymers,bio-compatible metals, shape memory metals, resorbable polymers,bio-inert polymeric materials, thermoplastic polymers, thermosetpolymers or any combination of these materials.

As one detailed example, saddle member 50 may be fabricated from adeformable plastic material, such as polyetheretherketone (PEEK)polymer. Alternatively, saddle member 50 may be fabricated from anotherdeformable material selected from the group consisting of carbon fibercomposite polymers, UHMWPE, shape memory metals, resorbable polymers,bio-inert polymeric materials, thermoplastic polymers, thermosetpolymers and any combinations of these materials. In one implementation,the material used to comprise saddle member 50 will have a flexuralmodulus that is equivalent or similar to the flexural modulus ofstabilization member 30. One possible range of the flexural modulus ofsaddle member 50 is from about 30 to 115 MPa.

Bone anchor 40 is typically configured as a bone screw, althoughalternative bone anchors may be utilized including bone fixation posts(not shown), bone staples (not shown), hooks (not shown), and moveablehead screws (not shown). It should be understood by those skilled in theart that the bone anchor-coupling mechanism structures described hereinare presented by way of example only and that other configurations maybe used, including coupling mechanism 10 being configured integrallywith bone anchor 40.

FIGS. 4 & 4A depict an alternate embodiment of a bone stabilizationsystem, in accordance with an aspect of the present invention. Thisembodiment is similar to the bone stabilization system embodiment ofFIGS. 1-3; however, saddle member 50 of the initial embodiment isreplaced by a posted member 150, and the seating member 20 is replacedby a seating member 120 configured in one embodiment as shown in FIGS. 4& 4A. More particularly, this bone stabilization system includes acoupling mechanism 110, a locking device (comprising seating member 120and a separate posted member 150), a stabilization member 130, and abone anchor 140. When in use, bone anchor 140 is placed within anindividual vertebrae, with a coupling mechanism 110 attached thereto.Coupling mechanism 110 is appropriately dimensioned to receivestabilization member 130, which spans one or more levels of the effectedvertebral region. In this embodiment, coupling mechanism 110 againincludes two upwardly projecting arms which have (by way of example)threads 112 on an inner surface thereof for threadably receiving seatingmember 120 of the locking device.

As shown, seating member 120 includes a threaded portion 122 and a drivetool receiving portion 124 having, in this example, a hexagonal-shapedperimeter. A central cannulation or opening 126 extends through seatingmember 120 and is sized to receive a post 155 of posted member 150.Those skilled in the art will understand from the description providedherein that multiple posts 155 may be provided extending from aninterface member 165 of the posted member 150, in which case multiplecorresponding openings 126 would be provided within seating member 120.Various posted member embodiments are presented below with reference toFIGS. 7A-10C. In the embodiment illustrated in FIGS. 4 & 4A, one centralpost 155 extends from a proximal surface 161 of interface member 165 andis received within opening 126 of the seating member. The distal surface162 of interface member 165 is saddle-style contoured to facilitatephysical contact with stabilization member 130.

Post 155 is sized to extend from interface member 165 a sufficientdistance D to allow a surgical drive instrument to couple thereto tofacilitating holding the posted member and the seating member together,as well as to hold the posted member fixed and in physical contact withthe stabilization member to facilitate control of the stabilizationmember as the seating member 120 is operatively engaged with thecoupling mechanism 110. Various embodiments of a surgical drive tool arepresented below with reference to FIGS. 13-15A.

The distance D that the post extends from the interface member may varywith the implementation, and may even extend a distance greater than theheight H of the seating member, as well as be provided with a break-offline to facilitate removal of a break-off portion of the post afterseating of the seating member within the coupling mechanism. In theembodiment of FIGS. 4 & 4A, post 155 is shown to extend from interfacemember 165 a distance equal to the height of seating member 120, as bestshown in FIG. 4A, wherein post 155 extends within the central opening126 of seating member 120.

FIGS. 5 & 5A depict an alternate embodiment of a locking device for abone stabilization system, which again includes a bone anchor 140, astabilization member 130 and a coupling mechanism 110 configured tocouple the stabilization member to the bone anchor by cradling thestabilization member as shown. The stabilization member 130 may extendthrough any number of coupling mechanism/bone anchor assemblies. In thisembodiment, the locking device comprises a seating member 120 such asdescribed above in connection with FIGS. 4 & 4A, and an alternateembodiment of a posted member 250. In this alternate embodiment, postedmember 250 includes an interface member 265 and a post 255 extendingfrom a proximal surface 261 thereof. The distal surface 266 of interfacemember 265 is again saddle-style contoured to physically engage aportion of the outer surface of stabilization member 130. Post 255includes a circumferential break-off line 272 around the perimeterthereof which defines a break-off portion 270. The break-off line 272 isdisposed in this embodiment a distance from proximal surface 261 equalto or less than the height of seating member 120. This is illustrated inFIG. 5A wherein post 255 has been broken along break-off line 272 andbreak-away portion 270 (see FIG. 5) has been removed. The remaining post255 portion is disposed within the opening provided within the seatingmember 120.

In operation, a surgical drive tool component engages post 255 asseating member 120 threadably engages coupling mechanism 110 to hold theposted member fixed and in physical contact with stabilization member130 to maintain the stabilization member in a fixed position duringplacement of the locking device in operative position with the couplingmechanism. When in operative position, the locking device locks theposted member, and in particular, interface member 265 between seatingmember 120 and stabilization member 130 to fixate the stabilizationmember relative to the coupling mechanism.

FIG. 6 depicts an alternate embodiment of a bone stabilization systemwherein a bone anchor 340 includes a head 341 which is pivotally engagedby a coupling mechanism 310 such that the coupling mechanism-to-boneanchor interface is polyaxial, which may allow easier positioning of thebone stabilization system relative to patient geometry. The couplingmechanism is again sized to receive a stabilization member 130, and inthis embodiment, the locking device is shown operatively positioned withthe seating member 120 fully threadably engaged with the couplingmechanism 310. When fully engaged, posted member 150 is positionedbetween the seating member 120 and the stabilization member 130, withthe interface member 165 in physical contact with the stabilizationmember and the at least one post 155 extending therefrom being receivedwithin a corresponding at least one opening 126 in the seating member120.

FIGS. 7A & 7B depict another embodiment of a posted member 400, inaccordance with an aspect of the present invention. In this embodiment,posted member 400 again comprises an interface member 410, with at leastone post 420 extending a distance D from a proximal surface 411 thereof.The distal surface 412 of interface member 410 is shown to be a planarsurface, by way of example. The distance D that the post extends fromthe proximal surface 411 of interface member 410 is sized to facilitateengagement of a surgical drive tool with the post to facilitate handlingof the posted member and seating member together, as well as tofacilitate control of the stabilization member as the seating memberoperatively engages the coupling mechanism to secure the stabilizationmember within the coupling mechanism with the posted member disposedbetween the seating member and the stabilization member. Thestabilization member can comprise a number of cross-sectionalconfigurations, including circular, oblong, or elliptical, etc. Thus,the posted member facilitates holding the stabilization member in adesired position within the coupling mechanism as the locking device issecured to the coupling mechanism. The distance D can vary, and is inone example at least one-half the height of the seating member. In theembodiments illustrated in FIGS. 4-6, the seating member includes one ormore openings extending therethrough which allow the surgical drive tool(see FIGS. 13-15A) to engage the post to hold the post while the seatingmember is operatively positioned relative to the coupling mechanism.

FIG. 7C depicts the posted member of FIGS. 7A & 7B with the addition ofone or more protrusions 430 extending from distal surface 412 ofinterface member 410. Protrusion(s) 430 may be rounded or pointed andconfigured to facilitate interfacing of the posted member to thestabilization member. For example, if the stabilization member ismanufactured of a biocompatible metal, then protrusions 430 may assistin fixating the stabilization member relative to the posted member.

FIGS. 8A & 8B depict alternate embodiments of the posted member, whereina post 520 again extends from the proximal surface 511 of an interfacemember 510. In this embodiment, the distal surface 512 of interfacemember 510 is saddle-style contoured to conform and physically contactto a portion of the stabilization member in a manner similar to theembodiment shown in FIGS. 4-5A. Further, in this embodiment post 520 isconfigured with a circumferential break-off line 521 disposed around theperimeter of the post. This break-off line can be formed, for example,by circumferentially removing material from post 520 at the desiredlocation. In FIG. 8A, break-off line 521 is shown intermediate the endsthereof, while in FIG. 8B, break-off line 521 is at the interfacebetween post 520 and interface member 510.

In the embodiment of FIG. 8A, after placing the seating member inoperative engagement with the coupling mechanism, the surgical drivetool is employed to twist off break-off portion 522 of post 520. Theremaining portion of post 520 in FIG. 8A extends from surface 511 adistance into the seating member less than or equal to the height of theseating member, as explained above in connection with the embodiments ofFIGS. 4-6. In the embodiment of FIG. 8B, the entire post is thebreak-off post portion 522, and is removed after placement of theseating member in operative engagement with the coupling mechanism,leaving only interface member 510 between the seating member and thestabilization member. In this implementation, proximal surface 511 ofinterface member 510 is substantially planar after break-off of thepost. Twist off of the break-off post portion along the circumferentialbreak-off line can be designed to occur at a particular torque valueapplied to the post. Considerations for the determination of this torquevalue include the type of material employed for the post, the diameterof the post, as well as the amount of material circumferentially removedfrom the post to define the circumferential break-off line.

FIGS. 9A & 9B depict further variations of the posted member, inaccordance with aspects of the present invention. In FIG. 9A, the postedmember again includes an interface member 610 and at least one post 620extending from a proximal surface 611 thereof. The distal surface 612 ofinterface member 610 is saddle-style contoured to conform to a portionof the stabilization member (not shown). In this embodiment, post 620includes multiple key slots 625 placed circumferentially about the postto facilitate interfacing of the surgical drive tool (not shown) withthe post, and thereby enhance holding of the post in fixed positionduring operative engagement of the seating member with the couplingmechanism.

FIG. 9B depicts an alternate embodiment of the posted member, wherein apost 630 again extends from interface member 610. In this embodiment,post 630 includes barbs 635 extending radially outward from a break-offpost portion 632 thereof defined by a break-off line 631. Barbs 635 areconfigured to facilitate interfacing of a surgical drive tool to thepost during operative engagement of the seating member to the couplingmechanism to hold the posted member in fixed physical contact with thestabilization member, and thereby maintain the stabilization member infixed position within the coupling mechanism. Additionally, barbs 635facilitate retention of break-off post portion 632 within the surgicaldrive tool after twist-off of the break-off post portion from theremaining portion of the posted member.

FIGS. 10A and 10B & 10C depict further geometric post variations for theposted member. In the top plan view of FIG. 10A, the posted member isshown to comprise an interface member 610′ from which a triangular post640 projects. In this example, post 640 is again an elongate postextending from interface member 610′ in a manner similar to the postsdescribed above. However, in this embodiment, post 640 has a triangulartransverse cross-section as shown in the plan view. Any desiredgeometric configuration can be employed for the post. FIGS. 10B & 10Cdepict an alternate embodiment wherein a hexagonal-shaped post 650extends from interface member 610′. Other transverse cross-sections forthe post could include circular, rectangular, oblong, etc.

FIGS. 11-12C present various embodiments of a seating member to beemployed in a locking device, in accordance with aspects of the presentinvention. FIG. 11 again repeats seating member 120 from FIGS. 4-6. Apartial depiction of post 155 is shown to extend within center opening126 of seating member 120. In one implementation, center opening 126extends through seating member 120. Seating member 120 further includesa threaded portion 122 and a drive tool receiving portion 124, which inthis embodiment has a hexagonal-shaped outer perimeter to be engaged bya corresponding hexagonal-shaped drive tool (not shown).

Seating member 120 may be fabricated from a titanium alloy, for example,the alloy Ti-6Al-4V. Alternatively, the seating member may be fabricatedfrom one or more of CP titanium, cobalt-chromium, a 300 series stainlesssteel, carbon fiber materials, carbon fiber composites, resorbablepolymers, bio-inert polymeric materials, thermoplastic polymers,thermoset polymers, or any combination of these materials. The postedmember may be fabricated of the same material as the seating member, ordifferent material. For example, the posted member may be fabricated ofa material which elastically deforms, and thereby fixedly secures thestabilization member when the locking device is threadably advanced intothe coupling mechanism. By way of example, the posted member could beformed from a deformable plastic material, such as polyetheretherkeytone(PEEK) polymer. Alternatively, the posted member could be fabricatedfrom another deformable material comprising carbon fiber compositepolymers, UHMWPE, shape memory metals, resorable polymers, bio-inertpolymeric materials, thermoplastic polymers, thermoset polymers, or anycombination of these materials. Still further, the posted member couldbe fabricated from a biocompatible metal or metal alloy.

FIG. 11A depicts an alternate embodiment of a seating member 720, and apartial post 155 extending into a center opening 726 provided therein.In this embodiment, a break-off line 721 is defined circumferentiallyabout seating member 720 between threaded portion 722 and drive toolreceiving portion 724. Drive tool receiving portion 724 is againprovided with a hexagonal-shaped perimeter to facilitate coupling of thedrive tool to the seating member. Aligned with break-off line 721 is abreak-off line 151 in post 155. With this embodiment, once the seatingmember is fully operationally engaged with the coupling mechanism tofixate the stabilization member, the drive tool (described below) isemployed to break off both the drive tool receiving portion 724 of theseating member, and the break-off post portion of post 155 at thealigned break-off lines 721 & 151.

FIGS. 12A & 12B depict a further embodiment of a seating member for alocking device, in accordance with an aspect of the present invention.In this embodiment, seating member 820 includes a threaded portion 822and a drive tool receiving portion 824. As shown, drive tool receivingportion 824 is configured with an internal hexagonal-shaped opening 828extending therein. The hexagonal-shaped opening 828 in this example isaligned with the post receiving opening 826, and depending upon theimplementation of the surgical drive tool, the post (not shown) of theposted member may extend into hexagonal-shaped opening 828, or eventhrough opening 828, and thereby extend through the seating member intothe drive tool when the surgical drive tool engages the seating member.(In this regard, see FIGS. 13& 14.) FIG. 12B depicts a top plan view ofseating member 820, wherein the hexagonal-shaped internal opening 828 isillustrated within the tool receiving upper portion 824 of the seatingmember.

FIG. 12C depicts a top plan view of an alternate embodiment of a drivetool receiving portion 834 of a seating member. In this embodiment,receiving portion 834 has an internal hexalobular-shaped opening 838 forengagement by a surgical drive tool (not shown). As in the embodiment ofFIG. 12A, the post receiving opening (not shown) within the seatingmember may be aligned with internal hexalobular-shaped opening 838 toallow the post of the posted member to extend into, or even through, thedrive tool receiving portion 834 of the seating member.

FIG. 13 depicts one embodiment of a surgical drive tool 900 (inaccordance with an aspect of the present invention) shown operativelyengaging a seating member 720 of a locking device, which is fullythreadably coupled to a coupling mechanism 110 interfacing stabilizationmember 130 to a bone anchor 140. As shown, drive tool 900 includes afirst component 910, such as a rotatable outer shaft, which isconfigured (in one embodiment) with a hexagonal-shaped opening sized toreceive the drive tool receiving portion of seating member 720. A secondcomponent 920, for example, comprising an inner shaft, includes postreceiving opening 925 with barb-receiving indents 926 in an inner wallthereof configured to receive a barbed post 630 of the posted member. Inthis example, the posted member is assumed to comprise a configurationsimilar to that described above in connection with FIG. 9B. The surgicaldrive tool 900 further includes a torque driver connection 930 which canbe employed to selectively lock the first and second components 910 &920 together so that the component 920 turn together. This feature ofthe surgical drive tool is employed to facilitate twist-off break-awayof the drive tool receiving portion of seating member 720, as well asthe break-away post portion of post 630, at the break-off line 721 ofseating member 720 and the aligned break-off line of the post. Forexample, after threadably engaging seating member 720 fully intocoupling mechanism 110, torque driver connection 930 may be employed tolock the first and second components 910 & 920 together, after which asufficient torque is applied to twist off the drive tool receivingportion of seating member 720 along break-off line 721 and the break-offportion of post 630 at the aligned break-off line.

FIGS. 14 & 14A depict an alternate embodiment of a surgical drive tool1000 (in accordance with an aspect of the present invention), shownoperatively engaging a seating member 720 of a locking device, which isfully threadably coupled to a coupling mechanism 110 interfacingstabilization member 130 to a bone anchor (not shown). Drive tool 1000includes a first component 1010, such as a rotatable outer shaft,configured with a hexagonal-shaped internal opening sized to receive thedrive tool receiving portion of seating member 720, and a secondcomponent 1020, such as an inner shaft configured with an opening sizedto receive a break-off portion 522 of a post 155 of the posted member.

In this embodiment, the first and second components are interconnectedby a gear and pawl mechanism 1040. As shown in the cross-sectional viewof FIG. 14A, the gear and pawl mechanism 1040 includes a gear 1042affixed to second component 1020 and a pawl 1044 mounted via a bracket1046 to first component 1010. The gear and pawl mechanism 1040 isconfigured to allow first component 1010 to freely rotate in onedirection to facilitate threadable engagement of the seating member 720with coupling mechanism 110. Once fully engaged, a sufficient torque isapplied to the first component to break off the drive tool receivingportion of seating member 720 along break-off line 721. By turning thefirst component 1010 in an opposite direction, the gear and pawlmechanism 1040 locks, allowing the application of a sufficient torque tothen twist off the break-off portion 522 of post 155. As shown, pawl1044, which is either external or internal the first component, isprovided with a handle 1048 to allow for release of the pawl from thegear.

FIG. 15 depicts another embodiment of a surgical drive tool 1100, inaccordance with an aspect of the present invention. This surgical drivetool is similar to the tool embodiment of FIG. 13, with the torque driveconnection being shown in greater detail in FIG. 15. As shown, a firstcomponent 1110, such as a rotatable outer shaft, has an opening in oneend sized to engage a drive tool receiving portion of a seating member(not shown). The surgical drive tool 1100 further includes a secondcomponent 1120, comprising an inner shaft having an opening sized toreceive a portion of the post of the posted member (not shown). A disc1122 resides at the proximal end of second component 1120 and includesmultiple openings 1123 therein (see FIG. 15A). The end opening 1121 insecond component 1120, which is shown to be hexagonal-shaped in FIG.15A, is sized and configured to receive a hexagonal-shaped posted membersuch as illustrated above in connection with FIGS. 10B & 10C (by way ofexample). The surgical drive tool further includes a cap 1130 affixed tofirst component 1110, and within which disc 1122 resides, and a torquedriver connection 1140, which in this embodiment comprises a platehaving a drive post 1144 and two members 1142 extending from oppositesurfaces thereof. When the surgical drive tool 1100 is in use, thetorque driver connection 1140 is selectively employed to lock movementof second component 1120 relative to first component 1110, in a mannersimilar to that described above in connection with FIG. 13. This isachieved by placing members 1142 of the torque drive connection 1140through appropriately aligned openings in cap 1130 (not shown) andopenings 1123 in disc 1122. By way of example, the proximal end of drivearm 1144 is square-shaped to mate to a square-shaped driver (not shown),rotation of which would cause the first and second component to rotatetogether.

In view of the above description, those skilled in the art will notethat a method for stabilizing a spinal column is presented herein. Thismethod includes: providing a bone stabilization system comprising a boneanchor, a stabilization member, a coupling mechanism, and a lockingdevice, wherein the coupling mechanism is configured to couple thestabilization member to the bone anchor, and the locking device isoperatively associated with the coupling mechanism, and wherein thelocking device further includes a seating member configured tothreadably engage the coupling mechanism and a posted member configuredto control the stabilization member as the seating member threadablyengages the coupling mechanism, the posted member comprising aninterface member and at least one post extending therefrom, and whereinthe seating member includes at least one opening therein; positioningthe stabilization member in the coupling mechanism; positioning theposted member with the at least one post thereof within the at least oneopening of the seating member, and threading the seating member into thecoupling mechanism while holding the at least one post of the postedmember fixed and in physical contact with the stabilization member,thereby maintaining control of the stabilization member as the seatingmember engages the coupling mechanism; and continuing to threadablyadvance the seating member into the coupling mechanism, thereby causingthe posted member to become fixed between the seating member and thestabilization member, and securing the stabilization member between theposted member and the coupling mechanism.

In further aspects, the method includes employing a surgical drive toolfor performing the threading of the seating member into the couplingmechanism and the holding of the at least one post of the posted memberfixed and in physical contact with the stabilization member. Thesurgical drive tool includes a first component configured to operativelyengage the seating member to facilitate the threading of the seatingmember into the coupling mechanism and a second component configured tooperatively engage the at least one post of the posted member tofacilitate holding of the at least one post of the posted member fixedand in physical contact with the stabilization member.

The method can further include breaking off at least one of a portion ofthe seating member after threadable engagement of the seating memberwithin the coupling mechanism, or a portion of at least one post of theposted member. Providing of the seating member can include providing acircumferential break-off line extending around the perimeter thereof,and continuing to advance the seating member can include continuing toadvance the seating member within the coupling mechanism until break offof a break-off portion of the seating member along the circumferentialbreak-off line thereof is achieved. Further, the providing can includeproviding the at least one post of the posted member with acircumferential break-off line extending around the perimeter thereof,and the method can further include breaking off a portion of the atleast one post after threadably advancing the seating member into thecoupling mechanism, and causing the posted member to become fixedlypositioned between the seating member and the stabilization member.

To summarize, those skilled in the art will note from the abovedescription that provided herein is an enhanced locking device for abone stabilization system, as well as surgical drive tools forinserting/extracting the locking device and surgical methods forstabilizing a column employing a bone stabilization system and theenhanced locking device. The bone stabilization system includes a boneanchor, a coupling mechanism, and a stabilization member, wherein thecoupling mechanism is configured to couple the stabilization member tothe bone anchor. The enhanced locking device includes a seating memberand a posted member. The seating member is operatively associated withthe coupling mechanism for securing a stabilization member within thecoupling mechanism, and includes at least one opening therein. Theposted member includes an interface member and at least one postextending therefrom. The posted member is configured for dispositionbetween the seating member and the stabilization member with the atleast one post extending from the interface member being received intothe at least one opening of the seating member when the seating memberis employed to secure the stabilization member within the couplingmechanism.

Advantageously, the at least one post is sized to facilitate handling ofthe separate seating member and posted member pieces, as well as tocontrol the stabilization member as the seating member operativelyengages the coupling mechanism to secure the stabilization member withinthe coupling mechanism with the posted member disposed between theseating member and the stabilization member. Numerous variations on theseating member and posted member designs, as well as various embodimentsof the surgical drive tool, are depicted and described herein.

By way of example, the distal surface of the interface member of theposted member can comprise a number of different geometries, includingplanar and saddle-style contoured. A saddle-style contoured geometrythat follows the outer periphery of the stabilization member isbeneficial for semi-rigid stabilization members because the surfaceallows the force on the stabilization member to be distributed acrossthe entire geometry. Those skilled in the art will note, however, thatthe geometric shape of the distal interface surface of the posted memberis not limited to the surfaces described herein. Further, the outerprofile of the interface member is not constrained to being enclosed bythe perimeter of the coupling mechanism. That is, the interface membermay extend past the through slots in the coupling mechanism.

The one or more posts of the posted member can be located along thecentral axis of the interface member, or offset therefrom. Based on loaddistribution of the locking device to the stabilization member, it maybe desirable to offset the one or more posts from the central axis ofthe interface member. Typically, the direction the posts could shiftwould either be cranial or caudal, based on how the bone anchor issituated. However, the post is not limited to these orientations. Byoffsetting the post from the center axis of the interface member, loadmay be distributed along the interface member, but allow for variableload characteristics to be present, for example, to maintain asemi-rigid stabilization member in a desired manner.

The surgical drive tool presented herein is designed to grip the outergeometry of the one or more posts of the posted member, as well as togrip the drive tool receiving portion of the seating member, eitherexternally or internally. The surgical drive tool may have a barb-styleor cam-style inner shaft that would grip the outer geometry of the post,locking it in place the further the post is inserted into the surgicaldrive tool. In addition, the surgical drive tool could have a one-wayclutch that would allow rotation of the drive tool in a direction fortightening of the seating member into the coupling mechanism, and if thedrive tool is rotated in the opposite direction from the “driving”direction, then the instrument tightens on the post to separate at leasta portion of the post from the posted member. The surgical drive toolmay also have an internal shaft with geometry such that it would gripthe upper most portion of the post, i.e., a hexagonal-style or ahexalobular-shaped geometry.

In use, the upper portion of the seating member is inserted and retainedwithin the surgical drive tool, after which the posted member isinserted through the seating member into the surgical drive tool. Thedrive tool grips the one or more posts via the external geometry of theposts and allows the seating member of the locking device to be held inplace between the posted member and the surgical drive tool. Once thelocking device has been seated into the coupling mechanism, the post isthen separated and removed, or the height of the post is reduced bytwist-off so that the remaining post height does not extend anunacceptable level past the seating member. Removal of the post could beperformed by a number of methods, including cutting of the post, oremploying a twist off technique such as described above.

Although the preferred embodiments have been depicted and described indetail herein, it will be apparent to those skilled in the relevant artthat various modifications, additions and substitutions can be madewithout departing from its essence and therefore these are to beconsidered to be within the scope of the following claims.

1-33. (canceled)
 34. A surgical drive tool for inserting/extracting alocking device of a bone stabilization system including a bone anchor, acoupling mechanism, and a stabilization member, wherein the couplingmechanism is configured to couple the stabilization member to the boneanchor, and wherein the locking device comprises a seating memberoperatively associated with the coupling mechanism for securing thestabilization member within the coupling mechanism, the seating memberbeing configured with at least one opening therein, and comprises aposted member including an interface member and at least one postextending therefrom, the posted member being configured for dispositionbetween the seating member and the stabilization member with the atleast one post extending from the interface member being received intothe at least one opening of the seating member when the seating memberis employed to secure the stabilization member within the couplingmechanism, and wherein the surgical drive tool comprises: a firstcomponent configured to operatively engage the seating member tofacilitate positioning of the seating member within the couplingmechanism; and a second component configured to operatively engage theat least one post of the posted member to facilitate maintaining theposted member fixed and in physical contact with the stabilizationmember as the first component is employed to secure the seating memberwithin the coupling mechanism, thereby securing the stabilization memberwithin the coupling mechanism between the posted member and the couplingmechanism.
 35. The surgical drive tool of claim 34, wherein the seatingmember comprises a threaded portion configured to threadably engage thecoupling mechanism, and wherein the first component rotatably engagesthe seating member to facilitate threading of the seating member intothe coupling mechanism, and the second component engages the at leastone post of the posted member to maintain the posted member fixed and inphysical contact with the stabilization member as the seating member isthreaded into the coupling mechanism.
 36. The surgical drive tool ofclaim 35, wherein the first component comprises an outer shaft and thesecond component comprises an inner shaft, the outer shaft engaging asurgical tool receiving portion of the seating member, and the innershaft engaging at least a portion of the at least one post of the postedmember, the outer shaft being rotatable to facilitate the threadedengagement of the threaded portion of the seating member to the couplingmechanism.
 37. The surgical drive tool of claim 36, further comprising alocking mechanism for selectively locking the inner shaft and the outershaft together, thereby forcing the inner shaft and outer shaft to turntogether.
 38. The surgical drive tool of claim 37, wherein the lockingmechanism comprises a gear and pawl apparatus, wherein with rotation ofthe outer shaft in a first direction, the pawl allows the gear torotate, while rotation of the outer shaft in a second direction locksthe pawl and gear and causes the inner shaft and outer shaft to turntogether.
 39. The surgical drive tool of claim 38, wherein the at leastone post comprises a post including a break-off post portion which isremoved after the seating member is employed to secure the stabilizationmember within the coupling mechanism, wherein the outer shaft isemployed to secure the seating member within the coupling mechanism byrotating the outer shaft in the first direction, and wherein thebreak-off post portion is removed by rotating the outer shaft in thesecond direction, causing the inner and outer shafts to turn together,thereby causing break-off of the break-off post portion, and wherein thepost has a transverse cross-section comprising one of a circularcross-section, a triangular cross-section, a rectangular cross-sectionor a hexagonal cross-section, and wherein the inner shaft is configuredto matably receive at least part of the break-off post portion.
 40. Thesurgical drive tool of claim 37, wherein the locking mechanism comprisesa mating plate having at least one arm configured for selectiveplacement through a first opening in a cap associated with the outershaft, and a second opening in a disc associated with the inner shaft,wherein placement of the arm through the first opening and the secondopening results in the inner shaft and the outer shaft turning together.41. The surgical drive tool of claim 37, wherein selective locking ofthe inner shaft and the outer shaft facilitates break-off of a portionof the at least one post along a circumferential break-off line providedin the at least one post.
 42. A method for stabilizing a spinal column,the method comprising providing a bone stabilization system comprising abone anchor, a stabilization member, a coupling mechanism, and a lockingdevice, wherein the coupling mechanism is configured to couple thestabilization member to the bone anchor, and the locking device isoperatively associated with the coupling mechanism, and wherein thelocking device further comprises a seating member configured tothreadably engage the coupling mechanism and a posted member configuredto control the stabilization member as the seating member threadablyengages the coupling mechanism, the posted member comprising aninterface member and at least one post extending therefrom, and whereinthe seating member comprises at least one opening therein; attaching thebone anchor with the coupling mechanism secured thereto to a vertebra ofthe spinal column; positioning the stabilization member in the couplingmechanism; positioning the posted member with the at least one postthereof within the at least one opening of the seating member, andthreading the seating member into the coupling mechanism while holdingthe at least one post of the posted member fixed and in physical contactwith the stabilization member, thereby maintaining control of thestabilization member as the seating member engages the couplingmechanism; and continuing to threadably advance the seating member intothe coupling mechanism, thereby causing the posted member to becomefixed between the seating member and the stabilization member, andsecuring the stabilization member between the posted member and thecoupling mechanism.
 43. The method of claim 42, further comprisingemploying a surgical drive tool for performing the threading of theseating member into the coupling mechanism and the holding of the atleast one post of the posted member fixed and in physical contact withthe stabilization member.
 44. The method of claim 43, wherein thesurgical drive tool includes a first component configured to operativelyengage the seating member to facilitate the threading of the seatingmember into the coupling mechanism and a second component configured tooperatively engage the at least one post of the posted member tofacilitate the holding of the at least one post of the posted memberfixed and in physical contact with the stabilization member.
 45. Themethod of claim 42, further comprising breaking off at least one of aportion of the seating member after threadable engagement of the seatingmember within the coupling mechanism or a portion of the at least onepost of the posted member.
 46. The method of claim 45, wherein theproviding further comprises providing the seating member with acircumferential break-off line extending around the perimeter thereof,and wherein the continuing further comprises continuing to advance theseating member until break off of a break-off portion of the seatingmember along the circumferential break-off line thereof.
 47. The methodof claim 46, wherein the providing further comprises providing the atleast one post with a circumferential break-off line extending aroundthe perimeter thereof, and wherein the method further comprises breakingoff a portion of the at least one post after threadably advancing theseating member into the coupling mechanism and causing the posted memberto become fixedly positioned between the seating member and thestabilization member.